endo-postdiag-imaging

name	endo-postdiag-imaging
description	This skill recommends performing an imaging study to assess tumor size, appearance, and parasellar extent once biochemical diagnosis of acromegaly is confirmed. Trigger when IGF-1 is elevated and GH fails to suppress to <0.4 µg/L during an oral glucose tolerance test.

Perform imaging after biochemical diagnosis of acromegaly

STEP 1 — Gather Information

Collect confirmed biochemical diagnosis: serum IGF-1 above age‑adjusted normal range and GH nadir ≥0.4 µg/L after 75g oral glucose tolerance test. Document any clinical features (e.g., acral enlargement, headaches) and screen for MRI contraindications (pacemaker, claustrophobia, ferromagnetic implants).

STEP 2 — Rule In / Rule Out

If IGF-1 is elevated and GH nonsuppressed (≥0.4 µg/L post‑OGTT), rule in acromegaly and proceed to imaging; otherwise rule out acromegaly and consider alternative diagnoses (do not order pituitary imaging for acromegaly work‑up).

STEP 3 — Classify or Stratify

Assess MRI suitability: if no contraindications, select MRI as the modality of choice; if MRI is contraindicated or unavailable, classify for CT scan. This decision determines the imaging protocol to be used.

STEP 4 — Decide

Order a pituitary MRI with 2‑mm slices (or CT scan if MRI contraindicated) to visualize tumor size, appearance, and parasellar extent prior to surgical planning.

Clinical Guardrails / Mimics / Pitfalls

Do not rely on CT when MRI is available; do not skip imaging before surgery; avoid mistaking an empty sella for a normal pituitary; recognize that routine MRI may miss microadenomas—use thin‑cut slices; never use imaging to establish the biochemical diagnosis; do not proceed to imaging if IGF‑1 and GH suppression tests are not diagnostic.

Concrete Clinical Example

A 48‑year‑old presents with shoe‑size enlargement and frontal bossing. IGF‑1 is 820 ng/mL (elevated) and GH is 1.8 µg/L after OGTT (nonsuppressed). Biochemical diagnosis confirmed. No MRI contraindications. A pituitary MRI with 2‑mm slices reveals a 14‑mm macroadenoma with right cavernous sinus invasion.

Source: Acromegaly: An Endocrine Society Clinical Practice Guideline, Endocrine Society, 2014, doi:10.1210/jc.2014-2700